The invention relates to a process for the preparation of 1,2-dichloroethane by oxychlorination of ethene, to a catalyst employed in this process, and to a process for the preparation of the catalyst.
1,2-Dichloroethane is nowadays produced on an industrial scale by oxychlorination of ethene. In this process, ethene is reacted with hydrogen chloride and oxygen in the presence of a copper catalyst. Processes both in the gas phase on solid or fluidized catalysts and in the liquid phase using dissolved catalysts are available for the reaction, although only processes in the gas phase have been used on an industrial scale (see Ullmanns Enzyklopxc3xa4die der technischen Chemie [Ullmann""s Encyclopedia of Industrial Chemistry], 4th Edition 1975, Volume 9, p. 428).
The present invention relates to an improvement to the fixed-bed process. In the fixed-bed process, the high exothermicity of the reaction causes problems which can, at relatively high space velocities as can occur in economical operation, result in the formation of so-called hot spots in the catalyst bed. The formation of such hot spots must be avoided under all circumstances since they are associated with deactivation of the catalyst by evaporation of the copper salt and damage to the catalyst moldings. For this reason, a catalyst bed with graduated activity profile is used in the fixed-bed processes of the prior art, with the activity of the catalyst bed increasing in the direction of flow. This is usually achieved by impregnating the catalyst with a graduated content of active components and, if desired, selective promoters. In addition to this, the catalyst bed is, in accordance with the prior art, diluted, at least in the reactor zones in which the driving force of the reaction is still very high, i.e. usually in the front region of the catalyst bed, with particles of an inert material, for example crushed graphite, tabletted or extruded graphite powder or non-impregnated catalyst support. Processes of this type are described in U.S. Pat Nos. 3,184,515 and 2,866,830.
However, the use of inert diluent materials such as graphite is accompanied by the significant disadvantage of an increased pressure loss, which has an effect, in particular, on use of low pressure-loss catalyst moldings and hinders material and heat transport in the axial direction. The conversion of pure graphite into low pressure-loss moldings is difficult and relatively expensive. The use of non-impregnated supports as diluent material is not recommended owing to the poor thermal conductivity, but in particular owing to the non-negligible activity of non-impregnated aluminum oxide supports for the formation of by-products. Excessive dilution of the active components on the support material is likewise unfavorable since this considerably impairs initiation of the reaction.
It is an object of the present invention to provide a process for the oxychlorination of ethene on a fixed-bed catalyst which manages without the presence of additional particles of an inert diluent material, even at high reactor space velocities.
We have found that this object is achieved by a process for the preparation of 1,2-dichloroethane by oxychlorination of ethene in the presence of a copper-containing fixed-bed catalyst comprising a bed essentially consisting of catalyst particles which comprise, at least partially, support material impregnated with an active component and, if desired, a promoter, where the catalyst bed comprises essentially no separate inert material for dilution.
A separate inert material is a chemically inert diluent material which is different from the catalyst particles and is not impregnated or cannot be impregnated. For the purposes of the present invention, inert material present in the catalyst particles is not a separate inert material. The term xe2x80x9cessentially consisting of catalyst particlesxe2x80x9d means that the bed consists of at least 80% by weight, preferably at least 90% by weight, particularly preferably at least 95% by weight, and especially 100% by weight, of the catalyst particles.